Huge radio telescope boasts supercomputer brain

One of the world's most powerful supercomputers is to be the brain of a revolutionary new radio telescope called LOFAR. The telescope will look back to the time of the very first stars, map our galaxy's magnetic field and perhaps discover the mysterious sources of high-energy cosmic rays.

Instead of one large rigid dish, LOFAR will use thousands of simple radio antennae. Their signals will be woven together at the University of Groningen in the Netherlands by STELLA, the new supercomputer, which was launched on Tuesday and is unofficially ranked as the third most powerful on the planet.

LOFAR needs its own supercomputer because it aims to detect radio wavelengths of up to 30 metres. Such long-wave radio images are blurry, and the only way to make them sharper is to build a vast array of detectors spread over hundreds of kilometres.

But that is not the only problem. A layer of Earth's upper atmosphere called the ionosphere bends these radio waves unpredictably - it makes any cosmic radio source twinkle - and with receivers scattered over a wide area the twinkling is disastrous, washing out the image completely.

The solution is to use some of the radio data to monitor the ionosphere, modelling its fluctuations with STELLA, and compensate for the twinkling effect. This has to be done in real time, which needs STELLA's huge computing power - 27.4 trillion operations per second.

Pyramid antennae

LOFAR's design works out relatively cheap, at about 150 million ($195 million). "Big dishes are expensive, as you need mechanics to move them," says Eugene de Geus, director of LOFAR. Instead, the team will build 20,000 antennas, each one a simple pyramid of copper wires with an amplifier at the apex tuned to the megahertz range.

The receivers will be scattered over an area 400 kilometres across, centred on the northern Netherlands. They will be connected by a fibre-optic network that will handle 22 terabits of data per second, equal to the entire telephone traffic of the US. "It is the world's largest FM radio," says de Geus.

So far, they only have 100 prototype antennae working, but de Geus hopes to have all 20,000 installed and hooked up within about three years. Then, LOFAR will be vastly more sensitive than any previous long-wave radio telescope.

One of its main objectives is to discover the end of the so-called cosmic dark age - a few hundred million years after the big bang. Astronomers want to find out what lit up first: stars, or more exotic objects called quasars?

LOFAR will also watch the formation of galaxies, map out the magnetic field of our galaxy and its neighbours, and detect high-energy particles hitting our atmosphere. The source of ultra-high-energy cosmic rays remains a mystery, but LOFAR should be able to trace a cosmic ray's radio trail back to the particle's origin.

Flaring brown dwarves

A similar, but even larger radio telescope called the Long Wavelength Array is being planned for construction in New Mexico. Patricia Henning, of the University of New Mexico, says the LWA will be especially good at probing the evolution of galaxy clusters.

She is also hoping to see radio flashes, perhaps from flaring brown dwarfs, extrasolar planets or neutron stars. "Once you open up a new part of the electromagnetic spectrum, you are bound to find new phenomena," she says.

The New Mexico site will have far less radio interference than LOFAR, which is sited in densely populated northern Europe. But de Geus thinks it would make more sense to build the LWA array in the southern hemisphere, where it could scan the southern sky.

He is also keen to escape radio interference: "It is the biggest threat to radio astronomy. For future developments we're looking at Western Australia - and the far side of the moon."

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.